Abstract: The activites of nitric oxide synthase(NOS) in cell bodies and terminals of neurons in the nigro striatal system were detected by using a histochemical method of nicotinamide adenosine dinucleotide phosphate diaphorase (NADPH-d) reaction in brain sections of the SD rat. The number of NOS positive neurons and density of the NOS positive terminals were counted under a DMRP biomicroscope. It was shown that the higher density of labled terminals and more labled neurons were located in the ventrolateral part of the striatum, while the lower density of terminals and less neurons in the dorsomedial part of the striatum. There were no terminals labled in the globus pallidus, substantial negra and thalamus. The results showed that the distributions of NOS positive neurons may have certain functional significance for motor regulation and certain parts of NOS positive terminals may be projected from the cerebral cortex.

Key words: nitric oxide synthase, NADPH diaphorase, substantia negra, striatum